Default clipboard setting

Setting the policy to 2 blocks sites from using the clipboard site permission. Setting the policy to 3 or leaving it unset lets the user change the setting and decide if the clipboard APIs are available when a site wants to use one. This policy can be overridden for specific URL patterns using the ClipboardAllowedForUrls and ClipboardBlockedForUrls policies. This policy only affects clipboard operations controlled by the clipboard site permission, and does not affect sanitized clipboard writes or trusted copy and paste operations.